Electromagnetic pumps for pumping molten metal



@3111; Buuvim JlU il mgw LAM mum-w FlP8502 R. MICHAUX Nov. 29, 1966ELECTROMAGNETIC PUMPS FOR PUMPING MOLTEN METAL Filed Aug. 26, 1963 5Sheets-Sheet l Fig.1

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ELECTROMAGNETIC PUMPS FOR PUMPING MOLTEN METAL Filed Aug. 26, 1963 3Sheets-Sheet 2 Fig. 2

Nov. 29, 1966 R. MICHAUX 3,288,069 ELECTROMAGNETIC PUMPS FOR PUMPINGMOLTEN METAL Filed Aug. 26, 1963 3 Sheets-Sheet 5 #wnvroe EAYMOA/DM/Cf/Al/X United States Patent 3,288,069 ELECTROMAGNETIC PUMPS FGRPUMPING MOLTEN METAL Raymond Michaux, Saint Germain-eu-Laye, France,assignor to Institut de Recherches de la fiiderurgie Francaise, SaintGermain-en-Laye, France Filed Aug. 26, 1963, Ser. No. 304,388 Claimspriority, application France, Sept. 7, 1962,

16 Claims. c1. 103-1 The present invention relates to the transportationof molten metal.

In particular, the present invention relates to the pumping of moltenmetal.

For some time now electromagnetic devices of diiferent types have beenused for pumping molten metals. Devices of this type have been used, forexample, to circulate metals of relatively low melting points, such assodium or potassium, and these devices have been used for coolingpurposes in certain nuclear reactors.

While attempts have been made to use such devices for metallurgicalpurposes in order to transport or cast molten metals of relatively highmelting points, great difficulties have been encountered in suchapplications, and up to the present time very little practical use hasbeen made of electromagnetic pumping devices for molten metals of highmelting points.

In general these devices use the same general principle of operation,which is to say the action of magnetic field on an electric current, inthis case a current traversing a stream of liquid metal, this principlebeing according to the well known law of Laplace. The force which actson the liquid is in a direction normal to the direction of the lines offorce of the field and the current which passes through the liquidelement.

There are in fact two types of electromagnetic devices which are usedfor transporting liquid metals, one of the types of devices acting byconduction (action) and the other acting by induction (reaction). Thedevices of the first type involve the circulation of a strong intensecurrent transversely through the stream of liquid metal, at a regionwhere the stream of metal is in an intense magnetic field, the lines offorce of this field are normal to the lines of current and to thelongitudinal axis of the stream of metal, so that in this way a forceacts on the stream of metal parallel to the longitudinal axis thereof.It the magnetic field is continuous, either as the result of a magnet orof a winding through which current flows continuously, the current whichtraverses the metal will also be continuous. Both the current and thefield can be equally alternating and of the same frequency, and in thiscase the phases are adjusted in such a way that the mean force acting onthe metal is a maximum in the desired direction. Devices of this generaltype are satisfactory for metals of low melting points, provided thatthere is available a material which is a good electrical conductor,sufficiently refractory, and incapable of being attacked by the moltenmetal so that it can constitute contacts for the passage of electriccurrent through the molten metal. The problems encountered in suchsituations are often very difficult to solve.

With the second type of devices referred to above, the windings aretraversed by an alternating current providing suitable magnetic fieldswhich give rise to induced currents in the stream of metal, and thereaction of these currents on the magnetic fields creates the pumpingforces provided that the induced currents are suitably oriented. Withinthis latter group of devices it is possible to distinguish betweenrepulsion devices in which a ring of liquid metal constitutes theshort-circuited secondary of a transformer of which the primary is awinding traversed by an alternating current, and devices having ashifting field in which the windings are situated along the stream ofmetal and are traversed by a suitable alternating current in generalthree-phase, providing a magnetic field which shifts or slides in thedirection in which the stream of metal extends while passing normallytherethrough. This inductive type of shifting field is analogous to thefield of an asynchronous induction motor, particularly of thesquirrel-cage type, and the present invention is particularly applicableto an electro magnetic, liquid metal pump which utilizes such a shiftingfield.

In devices of this type the reaction of the current induced in the metalon the inductive field transforms itself into a pressure within themolten metal itself. Such an arrangement is extremely simple because itis unnecessary to circulate an electrical current in the metal by meansof an exterior source. However, in order to obtain a pumping pressurewhich is sufficiently high for practical industrial purposes it isessential to orient the induced currents in the stream of metal, andthis prob lem is difiicult to solve. Thus, elongated bars which havevery high electrical conductivity may be placed in contact with thestream of metal extending in the same general direction as the stream ofmetal for the purpose of orienting the induced currents. If suchmeasures are not taken the induced currents would necessarily close uponthemselves and since they do not find a path of least resistance in thestream of metal they form instead an infinite number of small eddycurrents which oppose each other. Thus, by placing at each side of thestream of molten metal elongated bars of very low electrical resistancein contact with the stream, it is possible for the lines of current toclose upon themselves at the exterior of the stream of metal while theselines of current become oriented normally to the longitudinal axis ofthe stream of metal taking the shortest path from oneelectrically-conductive bar at one side of the stream of metal throughthe stream to the other electrically-conductive bar at the other side ofthe stream of metal. Thus, such electrically-conductive bars have withrespect to the stream of metal the same relationship as theshort-circuiting rings connecting the rotor bars of a squirrel-cagemotor.

Thus, the problem of making electrical contact between such bars and themolten metal is common to devices of the above groups. However, theproblem is a 'ditficult one to solve inasmuch as the molten metal has ahigh melting point. For example, it is desirable to be able toelectromagnetically pump a metal such as steel, and with inductiondevices of the above type it is essential that the lateral,electrically-conductive bars have an extremely low resistance relativeto the resistance of the molten metal itself. It is highly desirable tobe able to use such metals as copper or silver for theelectricallyconductive bars, but unfortunately these materials do nothave high melting points and thus they cannot be placed in contactdirectly with molten steel, for example.

It is accordingly a primary object of the present invention to provide aprocess and apparatus which make it possible to electricallyinterconnect a molten stream of metal which has a high melting pointwith electrical conductors of relatively low melting points and very lowelectrical resistances, so that in this way it becomes possible toprovide the desired pumping efficiency which makes the electromagneticpumping of molten metal of high melting points economically feasible.

In particular, it is an object of the invention to provide a process andapparatus which can reliably maintain over a long period of time anelectrical connection between a molten metal of high melting point andelectrical conductors of low resistance and low melting points.

Also, it is an object of the invention to provide a process andapparatus which will make electrical connections of this type withoutproducing any undesired physical or chemical reactions between themolten metal and structure in contact therewith.

It is furthermore an object of the present invention to provide aprocess and apparatus which make it possible to electromagnetically pumpmolten steel while maintaining an electrical connection between suchmolten steel and electrically-conductive bars made of copper, forexample.

It is furthermore an object of the invention to provide a structurecapable of accomplishing the above objects while at the same time beingcomposed of relatively simple rugged elements which can be quickly andeasily assembled and disassembled and which will have a long operatinglife.

With these objects in view the invention includes, in an electromagneticpump for pumping a molten metal, an elongated outerelectrically-conductive bar of low resistance extending in the samegeneral direction as and spaced from but located adjacent a stream ofmolten metal, and an inner bar of substantially the same properties asthe molten metal in contact with the latter as well as with the outerbar to provide an electrical connection between the molten metal and theouter bar, the structure of the invention also including a cooling meanswhich provides for the portion of the inner bar which engages the outerbar a temperature sufiiciently low to maintain the inner bar at leastpartially in a solid state. The process of the invention includes thesteps of maintaining, in an electromagnetic pump for pumping moltensteel, a copper bar in electrical connection with the molten steel byway of a ferrous metal bar located between and engaging both the copperbar and the molten steel while maintaining the portion of the ferrousbar which engages the copper bar at a temperature on the order of 25 C.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a partly schematic transverse sectional view of one possibleembodiment of an electromagnetic pump according to the presentinvention;

FIG. 2 is a fragmentary schematic longitudinal partly sectionalelevation of the electromagnetic pump of FIG. 1;

FIG. 3 is a schematic illustration of the windings and electricalconnections of the pump of the invention; and

FIG. 4 is a fragmentary view on an enlarged scale of part of thestructure of FIG. 1.

The figures illustrate an electromagnetic pump designed to pump liquidsteel at a rate of flow which can attain 50 tons per hour under apressure of approximately atmospheres.

The stream of molten steel flows along a passage 1 which has arectangular cross section and which has an extremely small depth whilebeing of a width which is very great in relation to its depth. Thepassage 1 for the stream of molten metal is formed in part by a pair ofplates 1a and 1b which are made of materials which have extremely highmelting points, much higher than the melting point of steel, and whichhave an extremely great electrical and mechanical resistance. Forexample, the plates 1a and 1b which are spaced from each other as shownparticularly in FIGS. 1 and 4 may be made of a ceramic material, andzirconia has proved to be particularly suitable for the plates 1a and1b. It will be noted that the plates 1a and 1b have outer side edgeswhich are bevelled. These ceramic plates 1a and 1b are clamped betweentwo groups of transformer laminations 2a and 2b, which form the magneticarmatures. Above and below the passage 1 are located horizontalelectrically-conductive bars 3 which extend perpendicularly across thestream of metal, these bars 3 being situated within correspondinginsulated notches of the magnetic armatures 2 and being maintainedwithin these notches by means of wedges identical with those utilizedfor maintaining the windings of electric motors in their notches, andthese wedges are not illustrated in the drawings for the sake ofclarity.

The bars 3 are connected in series by means of exterior connections 4having a special form as shown particularly in FIG. 2, and they areformed into an undulating, imbricated, three-phase series windingaccording to the diagram shown in FIG. 3. In FIG. 3 the upper and lowerbars are shown in a plan view, although normally the two parts shown inFIG. 3 are placed one above the other. The connections are similar tothose of an induction motor, and the entire construction is the same asif the stator of an asynchronous, three-phase induction motor isunrolled so as to have a fiat configuration. The rotating field of suchan asynchronous motor is thus replaced in this case by the sliding orshifting field which shifts perpendicularly to the plane of FIG. 3 andwhich becomes displaced in a direction parallel to itself and parallelto the longitudinal axis of the stream of molten metal. The shiftingfield induces in the molten metal currents on which it exercises forceswhich entrain the metal and cause it to flow in the same direction asthe direction of displacement of the field. The windings are supplied atA, B, and C with current from a three phase network. The bars 3 as wellthe exterior connections 4 therebetween are hollow and are traversed bya cooling liquid.

The molten metal which flows through the pump has a high temperature onthe order of 1600 C. or more, so that the cooling is particularlyimportant. For this reason the disposition of electrically-conductivebars above and below the passage 1 is of particular advantage. Ineffect, besides reinforcing the field, which results from thisarrangement, this device has the advantage of producing a symmetricalcooling of the two magnetic masses against which the refractory plates1a and 1b are located.

As has been indicated above, the ceramic plates 1a and 1b are spacedfrom each other and define part of the passage 1 through which themolten metal flows, and a particular feature of the invention resides inthe structure which completes the passage 1 and which provides theelectrical connection between the molten metal andelectrically-conductive bars of low resistance as referred to above.Thus, there are situated between the plates 1a and 1b, a pair of innerelongated electrically-conductive bars 6 (FIGS. 1 and 4), and in thecase of molten steel, these bars 6 are also made of steel or at least ofa ferrous metal so that they will not have any undesired physical orchemical reaction with the molten metal. The inner bars 6 are inengagement at their outer side edges, which project beyond the plates inand 1b, with a pair of outer bars '7 which are preferably made of copperand which serve to orient the current in the manner described above. Asis apparent from FIGS. 1 and 4, the copper bars 7 are formed withsubstantially V-shaped grooves which receive the bevelled side edges ofthe refractory plates 1a and 1b, and in addition the copper bars 7 areformed with additional groove portions which receive the outer side edgeportions of the inner bars 6 which project beyond the plates 1a and 1b,and these bars 6 may be brazed to the outer bars 7, if desired. Thus, itwill be seen that the inner side edges of the bars 6 which are directedtoward each other define with the inner surfaces of the plates 1a and1b, which are also directed toward each other, the passage 1 throughwhich the molten metal flows in the form of a ribbon or sheet of moltenmetal of extremely small thickness and of relatively great width, andfurthermore it will be noted that with this arrangement the bars 6 whichare of the same properties as the molten metal are directly in contactwith the molten metal. Because of the high temperature of the moltenmetal it is necessary to provide an extremely effective cooling for thebars 6, and in accordance with the present invention a cooling means isprovided, this cooling means acting on r the bars 6 for maintaining themat least at their portions which engage the outer bars 7 at temperatureslow enough to maintain the bars 6 in a solid state at least in part. Thecooling means is formed by the outer portions of the outer bars 7. Thus,these outer portions of the bars 7 are hollow so as to form theelongated hollow conduits 8 through which a cooling liquid is adapted tocirculate. As is apparent particularly from FIG. 4 the passages 8 areclosed by plates 9 also of copper and brazed, as indicated at 23 in FIG.4, to the bars 7 so as to close the passages 8 through which the coolingliquid flows.

In order to maintain the bars 7 in the illustrated positions inengagement with the plates 1a and 1b, pushers 10 engage the bars 7 andpush them toward each other. A series of pushers 10 are arranged on eachside of the assembly with one row engaging one of the bars 7 and theother row engaging the other bar 7, and the details of each of thepushers 10 are shown most clearly in FIG. 4. Thus, it will be seen fromFIG. 4 that each pusher bar 10 acts on a fiber shim 22 to push thelatter against the closure plate 9 which in turn pushes the bar 7, and aspring acts on each bar 10. Thus, the bar 10 extends slidably through asuitable sleeve 21 located within a tubular housing 11, and at its endwithin the tubular housing 11 the bar 10 threadedly carries a ring 10aon which one end of the spring 20 presses, the other end of the spring20 engaging the closed end of the tubular housing 11 which is fixed tothe frame of the apparatus, so that in this way the several springs 20act on the several pushers 10 on both sides of the apparatus to urge onerow of pushers toward the other row of pushers and thus in this way thepair of bars 7 are urged toward each other. Because of the bevelled sideedges of the refractory plates 1a and 1b and the substantially V-shapedgrooves of the bars 7 which receive these bevelled side edges, thepushing of the bars 7 toward each other by the rows of pushers 10 urgesthe refractory plates la and 1b toward each other so that they pressagainst the bars 6 which maintain the plates 1a. and 1b spaced from eachother, and in addition it is to be noted that the laminations 2a and 2balso press against the plates 1a and 1b. The dimensions and location ofthe inner ferrous bars 6 are such that the are situated just outside ofthe magnetic field.

During the normal functioning of the apparatus they are directly incontact with the molten steel and thus as sure the desired electricalconnection between the copper bars 7 and the molten metal. The heat ofthe molten metal is of course transferred to the bars 7 through theinner bars 6, and the copper bars absorb the heat which is veryeffectively carried away by the circulation of the cooling water orother liquid in the conduits 8, the portion of the bars 7 which areformed with the conduits 8 forming the cooling means for cooling theouter edge portions of the bars 6 which are situated distant from themolten metal. Thus, the steel or other ferrous metal bars 6 are incontact with the molten metal which is at a relatively high temperature(on the order of 1600 C.) While at their outer edge portions these bars6 are maintained at a relatively low temperature on the order of C., sothat in this way with the cooling action properly regulated a veryeffective cooling is provided which guarantees that the bars 6 will bemaintained in the solid state. Actually, with proper cooling thereexists a boundary layer separating the molten steel and the solid steelof the bars 6, and with proper cooling it has been found that the bars 6do not melt.

The entire assembly is mounted on a frame 12 composed of members such asangle bars of H section, and the polar masses are maintained in place bymeans of sheets 13 which are fixed to the frame 12. A pair of transversebars 14 are connected to the top of the frame so that the entireassembly can be conveniently handled.

In order to obtain a magnetic field which is as intense as possible, thethickness of the ribbon of molten metal which flows through the deviceis maintained at a minimum. In an actual construction of the typeillustrated in the drawings the thickness of the passage 1 is in theneighborhood of 1 cut, and the width of the passage 1 is in theneighborhood of 20 cm., the space between the polar masses 2a and 2bbeing on the order of 5 cm. In other words, each of the plates 1a and 1bwill have a thickness of approximately 2 cm. and these plates will bespaced from each other by a distance of 1 cm. so that the total distancebetween the laminations 2a and 2b is 5 cm. At each end of the device thepassage 1 (FIG. 2) cO-m-rnunicates with a conduit for the molten metalby way of a refractory fitting 15 having the general form of aparallepiped, each fitting 15 being formed with a flared passage 16communicating at its small end with the passage 1 and at its large endwith a suitable conduit which is not illustrated and which may have acircular section, the fittings 15 being situated within metallic casings17 which are fixed to the frame of the apparatus.

At its small end each passage 16 of course has a cross sectionalconfiguration corresponding to the cross sectional configuration of thepassage 1 so that the molten metal flows into and out of the passage 1from the passages 16 of the fittings 15 shown in FIG. 2 in a very smoothmanner.

As Was pointed out above, the device which is illustrated by way ofexample in the drawings is designed to provide a flow of molten steel ata rate of 50 ton-s per hour and at a maximum pressure in theneighborhood of 10 atmospheres. The construction which is designed forthis purpose is provided with 60 bars 3 above the passage 1 and an equalnumber below the passage 1, and these bars are traversed by electricalcurrent whose intensity can attain 3000 amperes. The total powerrequired ranges between and 200' kw.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofpumps differing from the types described above.

While the invention has been illustrated and described as embodied inelectromagnetic pumps, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an electromagnetic pump for pumping molten metal, in combination,an outer elongated electrically-conductive bar extending in the samegeneral direction as and located along a stream of molten metal which ispumped by the electromagnetic pump; an inner elongatedelectrically-conductive metallic bar of substantially the samecomposition as the stream of molten metal, said inner bar being locatedbetween and engaging both the stream of molten metal and the outerelectrically-conductive bar for electrically connecting the latter tothe stream of metal, the material of said outer electrically-conductivebar having a lower melting point and a higher electrical conductivitythan the material of said inner bar; and cooling means for cooling atleast that portion of said inner bar which engages said outer bar formaintaining 7 said portion of said inner bar :at :a temperaturesufiiciently low to maintain at least said portion of said inner bar ina solid state.

2. In an electromagnetic pump for pumping molten metal, in combination,an elongated outer electricallyconductive bar extending in the samegeneral direction as and located along a stream of molten metal which ispumped by the electromagnetic pump; an inner elongatedelectrically-conductive metallic bar of substantially the samecomposition as the stream of molten metal and located between andengaging both the stream of molten metal and the outer bar for placingthe latter in electrical communication with the stream of molten metal,the material of said outer electrically-conductive bar having a lowermelting point and a higher electrical conductivity than the material ofsaid inner bar; and cooling means for cooling that portion of said innerbar which engages said outer bar for maintaining said portion of saidinner bar at a temperature sufficiently low to maintain said inner barat least partially in a solid state.

3. In an electromagnetic pump for pumping molten metal, said pumpproviding a magnetic field which participates in the pumping of themolten metal, in combination, an outer elongated electrically-conductivebar extending in the same general direction as and located along astream of molten metal which is pumped; an inner electrically-conductivebar located between and engaging both the stream of molten metal and theouter bar for placing the latter in electrical communication with thestream of molten metal, said inner bar being located at least partiallybeyond the magnetic field of the pump; and cooling means for coolingthat portion of said inner bar which engages said outer bar formaintaining said portion of said inner bar at a temperature low enoughto maintain said inner bar at least partially in a solid state.

4. In an electromagnetic pump for pumping molten metal, in combination,an outer elongated electricallyconductive bar extending in the samegeneral direction as the stream of molten metal which is pumped andlocated adjacent but spaced from the stream; an innerelectricallyconductive bar of substantially the same composition as saidstream of molten metal, said inner bar being located between andengaging both the stream of molten metal and the outer bar for placingthe latter in electrical communication with the stream of molten metal,the material of said outer electricallyconductive bar having a lowermelting point and a higher electrical conductivity than the material ofsaid inner bar; and cooling means for cooling that portion of the innerbar which engages said outer bar for maintaining said portion of saidinner bar at a temperature sufficiently low to maintain at least saidportion of the inner bar in the solid state, said cooling meansincluding part of said outer bar which is hollow and through which acooling fluid is adapted to flow for maintaining the portion of theinner bar which engages the outer bar at said sufficiently lowtemperature.

5. In an electromagnetic pump for pumping molten metal, in combination,a pair of outer elongated hollow electrically-conductive bars; and apair of inner electrically-conductive metallic bars of the samecomposition as the molten metal, said pair of inner bars engaging andlocated between the outer bars and adapted to engage also a stream ofmolten metal which is pumped by the pump so as to place said outer barsin electrical communication with the stream of molten metal, theelectrical conductivity of said hollow outer bars being greater than theelectrical conductivity of said inner bars and said hollow outer barsbeing adapted to have a cooling fluid flowing thereth-rough formaintaining the portions of said inner bars which respectively engagesaid outer bars at temperatures sufiiciently low to maintain said innerbars in the solid state.

6. In an electromagnetic pump for pumping molten metal, in combination,a pair of spaced parallel plates of a material which has very littleelectrical conductivity and very high melting points substantiallyhigher than the temperature of the molten metal which is pumped; a pairof inner bars located between said plates at side edge portions of thelatter for maintaining said plates spaced from each other and fordefining with said plates an elongated passage through which a stream ofmolten metal is adapted to flow; a pair of outer elongated electricallyconductive bars engaging the outer side edges of said plates and alsoengaging said inner bars to be placed by the latter in electricalcommunication with the stream of molten metal; and cooling means forcooling those portions of said inner bars which engage said outer barsfor maintaining said portions of said inner bars at temperaturessufiiciently low to maintain said inner bars at least partially in asolid state.

7. In an electromagnetic pump for pumping molten metal, in combination,a pair of mutually spaced parallel plates of a material of electricalconductivity substantially lower than the electrical conductivity of themolten metal and a very high melting point substantially higher than thetemperature of the molten metal which is pumped; a pair of innerelectrically-conductive bars located between said plates at side edgeportions thereof and maintaining said plates spaced from each other,said bars defining with said plates an elongated passage through which astream of molten metal is adapted to flow; a pair of outer elongatedelectrically conductive bars engaging said plates at side edge portionsthereof and also engaging said inner bars to be placed by the latter inelectrical communication with the stream of molten metal, said outerbars being hollow so that a cooling fluid can flow through said outerbars for maintaining the portions of said inner bars which engage saidouter bars at temperatures sufliciently low to maintain said inner barsat least partially in a solid state.

8. In a pump as recited in claim 7, said inner bars respectively havingedge portions which project beyond said plates and said outer bars beingrespectively formed with grooves which receive said portions of saidinner bars.

9. In a pump as recited in claim 7, said outer bars being respectivelyformed with substantially V-shaped grooves which receive said side edgeportions of said plates, said side edge portions of said plates beingbevelled and mating with said grooves of said outer bars.

10. In a pump as recited in claim 9, spring means urging said outer barstoward each other so that the outer bars urge through said grooves andbevelled edges of said plates, said plates toward each other to pressagainst said inner bars.

11. In a pump as recited in claim 10, said inner bars having outer edgeportions projecting beyond said plates and said outer bars having grooveportions which receive said outer portions of said inner bars.

12. In a pump as recited in claim 11, said inner bars being made of amaterial which has substantially the same properties as the stream ofmolten metal.

13. In a process for electromagnetically pumping a molten metal, thesteps of maintaining in engagement with the molten metal a bar of amaterial which is electrically conductive and Whose properties preventany chemical or physical reaction between the molten metal and the bar;maintaining in engagement with the firstmentioned bar, but out ofcontact with the molten metal, a second bar of a material exhibiting agreater electrical conductivity but having a lower melting point thanthe material of said first mentioned bar; and cooling the firstmentionedbar to a temperature sufliciently low to maintain said first-mentionedbar at least partially in a solid state.

14-. In a process for pumping molten steel, the steps of maintaining inengagement with a stream of molten steel during pumping thereof aferrous bar while also maintaining in contact with the ferrous bar butout of contact with the stream of steel an elongated additional bar of amaterial of high electrical conductivity; and

9 10 cooling the ferrous bar to an extent suflicient to main- ReferencesCited by the Examiner tain the ferrous bar in the solid state.

15. In a process as recited in claim 14, said bar of UNITED STATESPATENTS high electrical conductivity being made of copper. 2,386,36910/1945 Thompson 103-1 16. In a process as recited in claim 15, theportion of 5 3,084,629 4/ 1963 Yevlck 103-1 said ferrous bar whichengages said copper bar being maintained at a temperature ofapproximately 25 C. LAURENCE V. EFNER, Primary Examiner.

1. IN AN ELECTROMAGNETIC PUMP FOR PUMPING MOLTEN METAL, IN COMBINATION,AN OUTER ELONGATED ELECTRICALLY-CONDUCTIVE BAR EXTENDING IN THE SAMEGENERAL DIRECTION AS AND LOCATED ALONG A STREAM OF MOLTEN METAL WHICH ISPUMPED BY THE ELECTROMAGNETIC PUMP; AN INNER ELONGATEDELECTRICALLY-CONDUCTIVE METALLIC BAR OF SUBSTANTIALLY THE SAMECOMPOSITION AS THE STREAM OF MOLTEN METAL, SAID INNER BAR BEING LOCATEDBETWEEN AND ENGAGING BOTH THE STREAM OF MOLTEN METAL AND THE OUTERELECTRICALLY-CONDUCTIVE BAR FOR ELECTRICALLY CONNECTING THE LATTER TOTHE STREAM OF METAL, THE MATERIAL OF SAID OUTER ELECTRICALLY-CONDUCTIVEBAR HAVING A LOWER MELTING POINT AND A HIGHER ELECTRICAL CONDUCTIVITYTHAN THE MATERIAL OF SAID INNER BAR; AND COOLING MEANS FOR COOLING ATLEAST THAT PORTION OF SAID INNER BAR WHICH ENGAGES SAID OUTER BAR FORMAINTAINING SAID PORTION OF SAID INNER BAR AT A TEMPERATURE SUFFICIENTLYLOW TO MAINTAIN AT LEAST SAID PORTION OF SAID INNER BAR IN A SOLIDSTATE.